An image sensor, such as a metal-oxide-semiconductor (MOS) image sensor is a photoelectric device which can convert optical images into electrical signals and has been widely applied in various consumer products such as, digital cameras, camcorders, personal communication systems (PCSs), game equipment, requiring for improved image resolution.
In order to satisfy the demands for finer image resolution capabilities, it is necessary to increase the pixel integration of MOS image sensors, and the size and pixel pitch of the constituent photoelectric transducer device, (e.g., a photodiode) shall be shrank. However, reduction in the physical size and pixel pitch of the photoelectric transducer devices may result in electrical and optical crosstalk between two adjacent photoelectric transducer devices, the sensitivity of the MOS image sensor is thus correspondingly reduced and, in the worst case, image distortion may occur.
Shallow trench isolations (STI) which are typically formed between two adjacent photoelectric transducer device in a conventional image sensor have been adopted by the prior art to reduce the possibility of electrical crosstalk. However, the STI which has limited depth may not possible to satisfactorily provide an electrical crosstalk barrier. Furthermore, the STI does not provide an effective optical crosstalk barrier when a backside image sensor is fabricated.
Therefore, it is necessary to provide an advanced image sensor and the fabricating method thereof to obviate the drawbacks and problems encountered from the prior art.